Brake shoe positioning device



June 28, 1960 B. E. HOUSE BRAKE SHOE POSITIONING DEVICE 2 Sheets-Sheet 1 Filed Jan. 15, 1956 XNVENTOR Bey/w 15 //005E MW9W ATTORNEY5 June 28, 1960 B. E. HOUSE BRAKE SHOE POSITIONING DEVICE 2 Sheets-Sheet 2 Filed Jan. 13, 1956 0 w y x United States Patent BRAKE SHOE POSITIONING DEVICE Bryan E. House, Ashtabula, Ohio, assignor to Rockwell- Standard Corporation, a corporation of Pennsylvania Filed Jan. 13, 1956, Ser. No. 559,044

1 Claim. (Cl. 188-78) This invention relates to improvements in vehicle brakes and has particular reference to a small diameter heavy duty hydraulic brake with floating shoes and an automatic shoe return adjustment.

A feature of the present invention is the provision in a brake mechanism of an automatic shoe return adjustment means which automatically compensates for lining wear to maintain shoe return movement relatively constant at an ideal setting during the entire brake lining life. The present invention is particularly useful in heavy duty brakes which are subject to relatively rapid brake lining wear, such as lift truck brakes, due to the elimination of the need for frequent manual brake adjustment.

The primary object of this invention is, therefore, to provide a heavy duty small diameter internally expansible brake mechanism having an automatic shoe return adjustment.

Another object is to provide, in an internally expansible brake mechanism, a shoe return adjustment for each brake shoe which is automatically set by shoe actuation as the shoe lining wears.

A further object is to provide an internally expansible brake mechanism having floating shoes which, during operation, automatically conform to the drum at all times during brake actuation and which have relatively constant balanced shoe actuating and return strokes throughout the brake lining life.

Another object is to provide an internally expansible brake mechanism having an automatic predetermined brake'adjustment effective throughout the entire brake lining life to eliminate entirely the need for manual brake shoe return adjustments.

A further object is to provide, in an internally expansible brake mechanism, a shoe return mechanism automatically adjustable and embodying a shoe slot adjusted crank which is spring friction position loaded to the brake backing plate.

Another object is to provide an internally expansible brake mechanism having oif center loading of the brake shoes by the shoe return spring to bias the shoes into bearing contact with the brake backing plate to dampen shoe vibration.

A further object is to provide, for use in a heavy duty internally expansible brake mechanism, a backing plate formed of a malleable casting having an integral abutment boss and an abutment boss top nib adapted to receive a shoe aligning and retaining spring lock washer.

These and other objects of the present invention will become more fully apparent by reference to the appended claim and as the following detailed description proceeds in connection with the accompanying drawings wherein:

Figure 1 is a partial end view of the brake mechanism of the present invention illustrating at the left the assembled brake structure and at the right the structure with the brake shoe and hydraulic wheel cylinder removed.

Figure 2 is a fragmentary sectioned view of the brake mechanism taken along line 2-2 of Figure 1.

Figure 3 is a fragmentary sectioned view of the autoice . 2 matic shoe return adjusting means, taken along line 3-3 of Figure 1.

Figure 4 is a partial sectioned view of the hydraulic cylinder in the brake taken along line 44 of Figure 1.

Figure 5 is a partial sectioned view of the shoe anchor abutment taken along line 55 of Figure 1.

Figure 6 is a fragmentary view of the pivoted end of one of the brake shoes.

Figure 7 is a fragmentary sectional view of the shoe web taken along line '77 of Figure 1 illustrating shoe return spring offset connecting means.

Referring now to the drawings, and more particularly to Figures 1 and 2, the illustrated brake assembly 10 comprises, in general, a brake drum 12, a pair of opposed internally expansible arcuate brake shoes 14 having linings 11 for braking engagement with the internal cylindrical brake drum surface 12, a hydraulically actuated wheel cylinder 16 and a backing plate 18. Brake drum 12 is integral with the wheel rim 13 which may be adapted, as shown, to receive a solid tire 15 or a pneumatic tire. Wheel rim 13 is secured by bolts 21 to the radial flange at wheel hub 23 which has an internally tapered bore and which is keyed at 25 to a similarly tapered end section 27 of axle shaft 22. Hub 23 is held on axle tapered end 27 by axle end nut 29 received on the threaded end of axle shaft 22.

Backing plate 18, which, in general configuration, is a flat disc, has a central boss having a coaxial aperture 26 through which axle shaft 22 extends. Oil seal 24 is mounted on axle shaft 22 Within aperture 20 to prevent loss of oil from axle shaft housing 26. Backing plate 18 is mounted on the end of axle shaft housing 26 by equiangularly spaced bolts 28 which pass through backing plate openings 39 and are threaded into aligned tapped holes in the end of housing 26. Opposed roller thrust bearings 32, which are retained in opening 34 at the end of axle shaft housing 26 by backing plate 18, journal the shaft 22. Opening 36 in backing plate 18 is provided to receive hydraulic wheel cylinder 16 which is bolted to backing plate 18 and has a boss 40 piloted in opening 36. Bleeder valve 42 and hydraulic coupling boss 44 integral with boss 40 project through the opening 36 as shown in Figure 2.

Backing plate 18 is preferably a malleable casting having an integral abutment boss 46 which projects axially from the plane of the main portion of the plate 18 into the brake 10. Boss 46 is formed with oppositely facing parallel planar shoe abutment faces 48, one for each shoe 14, and with an abutment boss top nib 50. Spring lock washer 52, having a diameter greater than the space between faces 48, is placed on nib 50 to retain the pivoted ends of shoes 14 in alignment with abutment faces 48 axially of the brake mechanism without restraining their movement along faces 48. Faces 48 are parallel to and equally spaced from a plane through the axis of the brake mechanism bisecting the wheel cylinder.

Shoes 14 are each formed with a generally cylindrical projection 54 forming an integral continuation of shoe web 56. Projections 54 project into the open ends of the hydraulic cylinder 16 to operatively engage the respective opposed hydraulic cylinder piston assemblies 58. Openings 69 are provided in the web 56 of each of the shoes 14 adjacent their actuated ends to receive the ends of shoe return spring 62. Each shoe web 56 is formed with a projection 64 offset toward the backing plate 18 so that the line of action of return spring 62 between openings 60 of each shoe 14 is off center toward backing plate 18 relative to the center plane of the shoes. By this construction, spring 62 is effective to bias shoes 14 into bearing contact with backing plate 18 to dampen shoe vibrations. Three equally circumferentially spaced beara set position;

(Figures 1 and 5) to'hold the curved abutment end 74 e achii'floatin'g" s'h'o Web '56 in rockable andslidable engagement with the respective abutment'boss facesx48.

The web-56 of each shoe 14 is provided with'an'elonlgatedrslot 76 adjacent to the offset projection 64 thereof A crank throw pin 78, whichis of a smaller diameter than therwidth of a slot 76, projects through the respective slots '76. Each pinj78.is' an integral part of a member 7 80" (Figures l 'and 3') with pin 78 at one end of a body 8 2 and a pivot pin'84 atr-the other end. Each pin,84 is received; i118. free 'fitithroughl a' backing plate opening f86a'ndf is shear'riveted the end-to hold' fiat washer to conform to the brake drum. When shoelining 11 is completely worn, the floating shoe 14 is low relative-to the brake and walls 98 and 96 of slot 76 contact pin 7 means for each brake shoe which is automatically set 9tt"in;-place.v A concav'e platespring92, preferably of V V the known as a BelleViile springwasher, which 'is resilientlyfcompressed between Washer90 and backing plate 1%, resiliently'biasesfriction surface 94 of crank throw member SO into frictional engagement with the backing piate' 18 to frictionally retain memberStiinits The diiference between the'diamete'r-of pin 78 and the width of the coac-ting slotg76, establishes the magnitude of theshoe'actuating" or return-movement for each brake shce l4: The difference-between the diameter'of'pin 78 and thewvidth' of'slot76 is'determined in design to provide a constant magnitude of play between the returned and actuated "positions" of the' brake shoes for the entire brake 'liningl ife. The l-imit'of return movement of shoe '14 when the brake is deactu'ated is established by-abutinent' of'slot edge 96 with pin 78 :because the force-of return spring- 62 is insufl'icient to overcome the frictional engaging -forees between member 80 and backing plate 'l8 holding member 80 stationary; However, as brake lining fl wears and brake' 10 is repeatedly actuated, hyr dtau'lic wheel cylinder 16 exerts'sufficientforce to-actuate shoes {14-and too'vercornethe frictional retaining force and move crank throw pin 78 progressively radially out ward consistent with shoe lining l-l wear; as slot'edge 98 V repeatedly; abuts; the pin 78 With each increment of rslioeilining wear the frictional rotational holding-engagement'betweenmernber 80 and-backing plate 1 8 is 'overcome andcrankthroW memberis rotateda compatible incremental distance to a new position in whichit is retained by frictionalrotationahholdingengagement with backing'plate'IS. 'Ihus-itis-appafentthatwhile the magnitnde o'fr'"brake -shoed i playi remains constant the loca- V tion efthe-retui n limit of the s'troke of each 'brakeshoe 'is-auto'maticallyadjusted outward throughout the entire brake lining life. This providesa' constant magnitude of brake shoemover'nent to fully engaged position :in contact with drum 12. t

fShoe-web- -slots76 are extended from end 100'to ejnd 102'to allowforthegradual floating shift of each shoe 14 consistent with lining 11 Wear from'rthelinitial floating V V V 'rockin'g' contact position ofshoe end 74 with the respective 1 abutnient surface s when shoe lining 11 is new as shown in Fi gureil withipin 78 adjacent slot end 100; As "lining '11- "wears; shoe-Q14 as a 'unit gradually shifts down ivardlyrelative'to the-mechanism as viewed in Figure 1 78 adjacent to end 102 of slot 76 as the brake is actuated and ,deactuated; a

In operation, when hydraulic cylinder 16 is actuated, shoe web projections 54 are pushed apart to urge shoes 14 into engagement with drum 12. Engagement of shoes 14 with drum '12 centers floatingshoes 14 with respect to the drum 12 and determines the positionof contact between rockable shoe end 74andabutment sa es-4s throughout shoe" lining 11;1ife.' g

From the foregoing it is, apparent that there is hereby provided a new improved small diameter heavy duty hydraulic brake with floating shoes and an automatic shoe return adjustment. It provides a shoe return adjustment by shoe actuation as the shoe lining years, It is an automatic brake" shoe returnadjus'tment determined at the engineering level for entire brake shoe lining life. pra vides a brake shoe return limiting crank member with a throw pin through a shoe'web slot which is spring frietion position load ed to th'e brakebacking plate. V i "The invention may be jernbodied'in other specificiorm's without departing from the spirit'or essentialcharacteristics thereof. The present embodiment is therefore to be considered in all respects as illustrative and not restrictive; the scope oftthe invention being indicated by the appended claimvrather than by the foregoing description; andt ail changes which come within the meaning'andirange of equivalency of the claim are therefore 'inten ded' to-lie embraced therein. i

? United" States Letters Patent is:

,7 In an internally expansible brake mechanisnn a sup port 'fona pair of self-centeringoppositely facing'arcnatc lined brake shoes, an abutment on said support' for en gagement by the brake shoes at one end thereof and adapted to'provide a rockable and slidable; pivot there'- ior, an actnatoron said support for engagement-with the'opposite ends of the brake shoes, said support being a" brake backing plate andsaid abutmentbeing a boss 7 formed integral with said backing plate and having spaced parallel shoe abutment faces and anraxiallyprojectin'g nib, and a spring lock washer mounted onand gripp'in'g said-nib; said washer beingof such size as to extendbeyond said abutment boss'shoe abutment'face'stoove rla'p the adjacent ends of the; shoes tomaintain axial align? inent between said' abutment and saidshoes.

V References Cited'in the file otpatent- UNITED STATES PATEN'rs 12,347,219 7 V S'ch eu-scans- A -22 19244 2,372,322 Goepfrich Mar.,27 ;1g45 25,09 H M r30a1 5 2 4 3 v He M mie- 451 2 7 8 28 L And s :SP'F- 9 2 15 '7 12,770 333 smir t Nov- 13 19:56 I N V v FOREIGN PATENTS f j V 

